Laws Flashcards
Inverse square law
Beam intensity is inversely proportionate to the distance from a source point
15 percent law increase
If your increase your KVP by 15% your exposure doubles
Maintenance for 15 percent rules
1
Reciprocity law
Same mAs from different MA and time
Example:
3mA • 2s= 6mAs
2mA • 3s= 6MAs
Window level
changes in brightness
15percent rules decrease
If you decrease your KVP by 15percent your expose rate is halved
Maintenance law
If you increase your KVP by 15 percent your exposure is halved
If you decrease your KVP by 15percent your expose is doubled
Window width
Controls the financial range on the monitor
High density
Lower your mas
Low density
Higher your mas
Photoelectric effect
Total absorption (gives you contrast)
High contrast (60kvp) Contrast Scale Shades of gray KVP
High contrast
Short scale
Few shades of gray
Low KVP
Low contrast (100kvp) KVP Shades of gray Scale Frequency Wavelength
Low contrast
Longer scale
More shades of gray
High KVP
H and d log 3 other names
Sensitometric
D log e
Primary
Photons from source point
Secondary
Scatter
Remnant
Photons from patient to IR
30% rule
30% change in mas is required for viable change in density
4-12%
4 to 12 percent in KVP is required for visible change in contrast
What relationships does mAs have with density
Directly proportionate
Increase in mAs has what affect on contrast
Negligible
Increase KVP has what affect on contrast
Goes down (more scatter)
Increasing source to image distance has what affect on contrast
Negligible
Increasing object to image distance has what affect on contrast
Increase less scatter
If I increase my grid what affect will that have on contrast
Increase (less scatter)
If I increase my collimation what affect will that have on contrast
Go up (less scatter)
Focal spot for both density and contrast are
Negligible
If I increase my filtration what will happen to my contrast
Decrease (more scatter)
If i increase my Part thickness my contrast will
Go down ( more scatter)
Increasing my Atomic # will have what affect on contrast
Increase ( adjacent densities)
Increasing Additive pathology will have what affect on contrast
Decrease ( more scatter )
If I increase my distructive pathology my contrast will
Increase adjacent densities
Increasing Radiopake and radiolucent will affect contrast how
Increase
The controlling factor for radiographic contrast is
KVP
The digital processing that produces changes I. The range of brightness, so it also is appropriate to use when controlling image contrast. What’s is this called
Window width
Two photographic factors allow detail to be seen
Density and contrast
An h & d curve demonstrating a steep curve represents image with
High contrast
Think steep curve
How’s does the use of filtration affect contrast
Low contrast
High energy radiation will result in
Long scale
Low contrast
Which of the following will occur if exposure time is increased
Density will increase
Which of the following factors will affect Radiographic density
Distance filtration anotomic size
Considering reciprocity law which of the following will occur if exposure time is decreased
Mas will increase
Which of the following affect radiographic density
(All)average atomic number
Thickness of anotomic part
Disease processes that decrease tissue density
